//定义一个委托

        public delegate int DoSomething(int count);

        //BeginInvoke 的回调函数

        private static void Execute(IAsyncResult async)

        {

            DoSomething temp = (DoSomething)async.AsyncState;

            int sum = temp.EndInvoke(async);

            Console.WriteLine("线程结束：值为" + sum);

        }

        /// <summary>

        /// 判断输入的整数是不是素数

        /// </summary>

        /// <param name="candidate">输入的整数</param>

        /// <returns>为素数返回true,否则返回false</returns>

        public static bool IsPrime(int candidate)

        {

            bool retVal = true;

            //使用递增方式会更有效率，

            //但是在演示取消功能时，使用递减的数字会更好。

            //for (int i = 2; i < candidate / 2; i++)

            for (int i = candidate / 2 + 1; i > 1; i--)

            {

                if (candidate % i == 0)

                {

                    retVal = false;

                    break;

                }

            }

            return retVal;

        }

        private static int maseggs(int count)

        {

            int result = 0;

            for (int index = 0; index < count; index++)

            {

                if (IsPrime(index + 1))

                {

                    result++;

                }

            }

            return result;

        }

      static void Main(string[] args)

        {

            DoSomething hidands = new DoSomething(maseggs);

            IAsyncResult async = hidands.BeginInvoke(100000, new AsyncCallback(Execute), hidands);

            //这里还有100行代码

            Console.WriteLine("消息获取成功");

            Console.ReadLine();

        }